This invention relates to dispensing apparatus; and more particularly, to apparatus for dispensing, de-areating and, if necessary, heating a viscous material.
Various systems for dispensing and for heating and dispensing viscous materials have been devised. Examples of such prior art systems are disclosed in the following U.S. Patents: U.S. Pat. Nos. 2,433,146 to Pyles; 2,630,248 to Hinz; 2,522,652 to Von Haase; 3,282,469 to Skonberg; and 3,412,903 to Van Riper, Jr., et al.
The aforementioned U.S. Pat. No. 2,433,146 to Pyles and U.S. Pat. No. 2,630,248 to Hinz both disclose dispensing apparatus using a follower plate that is lowered into a container of the material to be dispensed. Heating means for heating the material is not disclosed in either of these two patents.
The apparatus disclosed in the other three aforementioned U.S. patents all disclose heating means for changing the material to be dispensed from a solid or unpumpable viscous liquid to a pumpable less viscous liquid. Thus, U.S. Pat. No. 2,522,652 to Von Haase discloses apparatus that includes a heater plate but no follower plate. The apparatus disclosed in U.S. Pat. No. 3,282,469 to Skonberg includes a follower plate and a separate heater plate located below the follower plate and the apparatus disclosed in U.S. Pat. No. 3,412,903 includes a follower plate and a separate heater plate located below and spaced apart from the follower plate.
The apparatus disclosed in the aforementioned Pyles patent and the apparatus disclosed in the aforementioned Hinz patent are both designed to dispense material whose viscosity at normal operating temperatures is such that these materials can be dispensed without the application of heat to the materials to lower the viscosity before dispensing. Therefore, these patents are not concerned with any problems encountered in applying heat to the material to be dispensed. However, a problem that may be encountered with the apparatus of these two patents is the problem of entrapped air in the dispensed material. If air is entrapped in the material in the container, this entrapped air will be present in the form of air bubbles in the material after it is dispensed. These air bubbles entrapped in the material tend to break after the material is dispensed thereby causing voids or unsightly pits in the material. If this dispensed material is being used as a sealing or as insulating material, for example, any voids in the sealing bead of material or the insulating layer of the material cannot be tolerated since the material would not provide a suitable seal or insulator if holes are present. If the dispensed material is covered, pitting of the material is usually of no concern; however, if the dispensed material is visible, these pits caused by the entrapped air are unsightly and therefore, undesirable. Neither the apparatus of the aforementioned Pyles patent nor the apparatus of the aforementioned Hinz patent provide means for de-areating the material before it is dispensed.
As previously noted, the aforementioned Von Haase, Skonberg and Van Riper, Jr., et al, patents all disclose apparatus for dispensing material that requires the application of heat to render the material pumpable. In the apparatus of Skonberg and in the apparatus of Van Riper, Jr., et al, the heater plate and the follower plate are two separate and distinct plates. In the Von Haase apparatus a follower plate, which is desirable in such apparatus, is not provided.
As is the case with dispensing material that is pumpable without the application of heat, entrapped air is a problem encountered in dispensing materials that requires the application of heat to render the materials pumpable. These materials, incidentally, are commonly called hot melt materials. In fact, these hot melt materials, particularly some of the newer hot melt materials, contain a substantial amount of entrapped air. The manner in which these materials are manufactured tends to trap air into the materials. Manufacturers of these materials have expended substantial effort and sums of money attempting to de-areate the material. These attempts have met with little success. Thus, the materials are shipped to the users with a considerable amount of entrapped air and this entrapped air is then present in the materials as they are dispensed from the container. Neither the apparatus of the aforementioned Von Haase patent, nor the apparatus of the aforementioned Skonberg patent, nor the apparatus of the aforementioned Van Riper, Jr., et al patent, provides means for de-areating the material before finally dispensing the material.
Another problem not solved by any of the prior patents aforementioned is the problem of having to discontinue the dispensing operation during container changes. When the material in a container is depleted, a full container is substituted for the empty container. With the prior art apparatus the dispensing operation is temporarily interrupted during the container change over. Still another problem not solved by the apparatus of any of the patents above mentioned is that of continuous uniform flow of the material during dispensing. For materials with a relatively low viscosity it is not too difficult to provide a fairly uniform flow rate. As the viscosity of the material increases, it is difficult to obtain a uniform flow rate and prior art dispensing apparatus such as that disclosed in the aforementioned patents has not been able to provide a continuous uniform flow rate when dispensing viscous materials, particularly when dispensing the highly viscous hot melt materials. Thus, when the material is to be used as a sealant and dispensed in the form of a sealing bead, the bead is very often not uniform. Such a bead is unsightly and in some cases cannot be tolerated.
The apparatus of this invention overcomes the problems mentioned above. With the apparatus of this invention, the material is de-areated before dispensing, and the material is dispensed with a continuously uniform flow rate. Further, the apparatus of this invention provides for uninterrupted flow of the material during container changes and can be used to dispense materials pumpable at normal operating temperatures as well as hot melt materials without the use of a separate heater plate. The follower and heating means are fabricated as one integral unit.